The invention relates to an image sticking prevention circuit and, in particular, to an image sticking prevention circuit for a display power-off mode.
As shown in FIG. 1, a conventional liquid crystal display (LCD) 100 comprises a voltage converter 140, a gate driver circuit 110, a data driver circuit 120, and a pixel array 150. The pixel array 150 comprises a plurality of gate lines 112, a plurality of date lines 122, and a plurality of pixel driving circuits 130. The pixel driving circuit 130 comprises a driving transistor 132, a storage capacitor 134 and a liquid crystal cell 136. A gate and a source of the driving transistor 132 are respectively connected to one of the gate lines or data lines. When the gate drive circuit 110 raises a voltage of the gate line 112, the driving transistor 132 is turned on and a data signal on the data line 122 is transmitted to a drain of the driving transistor. Thereby, the data driver circuit 120 sends the data signal to the storage capacitor 134 via the data line 122 and the driving transistor 132. After the data signal is loaded into the storage capacitor 134, the gate driver circuit 110 decreases the voltage of the gate line 112 to its former level such that the liquid crystal cell 136 generates an image according to the data signal before the next data signal is loaded. However, when the LCD 100 enters a power-off mode, the data signal still remains in the storage capacitor 134, generating a residual image.
A conventional solution shifts the current to voltage (I-V) curve of the transistor 132 (as shown in FIG. 2) to the left such that a threshold voltage of the transistor 132 is close to 0V. Thus, the transistor 132 is turned on even if a gate voltage of the transistor 132 is close to 0V. As a result, the data signal stored in the storage capacitor 134 is released to the data line 122. Image sticking is thus prevented, but current leakage is a major concern due to the decreased threshold voltage.